System and method for controlling the deployment of jet engine thrust reversers

ABSTRACT

A system for controlling one or more jet engine thrust reversers includes a motor, a speed sensor, and a controller circuit. The motor is coupled to one or more jet engine moveable thrust reverser components for moving the one or more moveable thrust reverser components to at least a deployed position. The speed sensor is operable to sense the a rotational speed of the motor. The controller circuit has an output coupled to the motor for selectively energizing and deenergizing the motor in response to the speed sensor sensing that the rotational speed of the motor is, respectively, at or above a first predetermined rotational speed and at or below a second predetermined rotational speed. The system controls the deployment operation of the jet engine thrust reversers such that unwanted mechanical and electrical loads are avoided.

BACKGROUND OF THE INVENTION

The present invention relates to a system and method for controlling themovement of one or more jet engine thrust reverser components. Moreparticularly, the present invention relates to a system and method forcontrolling the movement of one or more jet engine thrust reversercomponents during a deployment operation of the thrust reversers.

When jet-powered aircraft land, the landing gear brakes and imposedaerodynamic drag loads (e.g., flaps, spoilers, etc.) of the aircraft maynot be sufficient to slow the aircraft down in the required amount ofdistance. Thus, jet engines on most aircraft include thrust reversers toenhance the stopping power of the aircraft. When deployed, thrustreversers redirect the rearward thrust of the jet engine to a forwarddirection, thus decelerating the aircraft. Because the jet thrust isdirected forward, the aircraft will slow down upon landing.

Various thrust reverser designs exist in the art, and the particulardesign utilized depends, at least in part, on the engine manufacturer,the engine configuration, and the propulsion technology being used.Thrust reverser designs used most prominently with turbofan jet enginesfall into three general categories: (1) cascade-type thrust reversers;(2) target-type thrust reversers; and (3) pivot door thrust reversers.As will be discussed more fully below, each of these designs employs adifferent type of “moveable thrust reverser component,” as that term isdefined herein below.

Cascade-type thrust reversers are normally used on high-bypass ratio jetengines. This type of thrust reverser is located at the engine'smidsection and, when deployed, exposes and redirects air flow through aplurality of cascade vanes positioned on the outside of the engine. Themoveable thrust reverser component in this design may include severaltranslating sleeves or cowls (“transcowls”) that are deployed to exposethe cascade vanes. Target-type reversers, also referred to as clamshellreversers, are typically used with low-bypass ratio jet engines.Target-type thrust reversers use two doors as the moveable thrustreverser component to block the entire jet thrust coming from the rearof the engine. These doors are mounted on the aft portion of the engineand form the rear part of the engine nacelle. Pivot door thrustreversers may utilize four doors on the engine nacelle as the moveablethrust reverser component. In the deployed position, these doors extendoutwardly from the nacelle to redirect air flow.

The primary use of thrust reversers is, as noted above, to enhance thestopping power of the aircraft, thereby shortening the stopping distanceduring landing. Hence, thrust reversers are primarily deployed duringthe landing process. More specifically, once the aircraft has toucheddown, the thrust reversers are deployed to assist in slowing theaircraft. Thereafter, when the thrust reversers are no longer needed,they are returned to their original, or stowed position.

When the thrust reversers are moved to the deployed position, thetranscowls or doors are moved until the actuator elements to which theyare attached reach a mechanical hard stop at the end of travel. In orderto prevent structural damage, the actuator elements should come to acontrolled stop against the mechanical hard stop. One problem associatedwith electromechanical thrust reverser systems in which the motive forcefor moving the thrust reversers is provided by electric motors, is thatthe aerodynamic loads imposed during aircraft landing tend, after acertain point during the deployment process, to accelerate the motors.Thus, if power is removed from the motors too soon before the actuatorelements reach their mechanical hard stop, the motors will “free-wheel,”being driven by the aerodynamic loads, up to speeds that may causesystem damage. Conversely, if power is supplied to the motor until theactuator elements hit the mechanical hard stop, the motor will try todrive the actuator elements past the hard stops and impose unwantedmechanical and electrical loads on the system.

Hence, there is a need for a system and method for controlling thedeployment of one or more jet engine thrust reversers that solves one ormore of the problems identified above. Namely, a system and method forcontrolling jet engine thrust reverser deployment that avoids one ormore of the following: unwanted motor accelerations due to aerodynamicloads imposed during thrust reverser deployment operations, unwantedmotor actuation too near to or after the hard stops have been reached toavoid unwanted mechanical and electrical loads and related systemdamage.

SUMMARY OF THE INVENTION

The present invention provides a system and method for controlling jetengine thrust reverser deployment that avoids unwanted mechanical andelectrical loads, and/or thrust reverser system damage. Specifically,and by the way of example only, the rotational speed of a motor that isprovided for moving the thrust reversers to the deployed position iscontinuously sensed and compared to predetermined rotational motor speedvalues. The speed that the motor is controlled to rotate at is reducedfrom a non-zero value to zero when the thrust reversers reach apredetermined position. When the sensed rotational speed is at or abovea first, upper predetermined rotational speed, power is applied tocontrol the speed of the motor to decelerate the motor to zero. When thesensed rotational speed is at or below a second, lower predeterminedrotational speed, power to the motor is removed. When power to the motoris removed, if the thrust reversers are not against their mechanicalstops, the aiding aero loads will cause the motor to accelerate to, orabove, the first predetermined rotational speed. This will cause powerto be supplied to the motor, thereby causing it to decelerate toward thesecond predetermined speed. When the rotational speed reaches the secondpredetermined speed, the motor will again be deenergized. Thus, when thethrust reversers reach the predetermined position, the thrust reverserswill limit cycle between the two predetermined speed limits until themechanical stop is reached in a controlled manner.

In one aspect of the present invention, a jet engine thrust reversercontrol system includes an electric motor, one or more moveable thrustreverser components, a speed sensor, and a controller circuit. Themoveable thrust reverser components are coupled to the motor, and aremoveable between a stowed position and a deployed position. The speedsensor is operable to sense at least a rotational speed of the motor andproduce a speed feedback signal. The controller circuit is coupled toreceive the speed feedback signal and is operable, in response thereto,to energize and deenergize the motor when the rotational speed of themotor is, respectively, at or above a first predetermined rotationalspeed and at or below a second predetermined rotational speed.

In another aspect of the present invention, a jet engine thrust reversercontrol system includes moving means, speed sensing means, andcontroller means. The moving means is for moving one or more moveablethrust reverser components to at least a deployed position. The speedsensing means is for sensing a rotational speed of the moving means. Thecontroller means is for (i) energizing the moving means when the speedsensing means senses that the rotational speed of the moving means is ator above a first predetermined rotational speed and (ii) deenergizingthe moving means when the speed sensing means senses that the rotationalspeed of the moving means is at or below a second predeterminedrotational.

In still another aspect of the present invention, a method ofcontrolling a jet engine thrust reverser system includes powering amotive force providing component to move one or more moveable thrustreverser components toward at least a deployed position. At least amovement speed of the motive force providing component is sensed. Powerto the motive force providing component is selectively applied andremoved in response to the sensed movement speed of the motive forceproviding component being, respectively, at or above a firstpredetermined movement speed and at or below a second predeterminedmovement speed.

Other features and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an aircraft engine;

FIG. 2 is a perspective view of portions of an engine fan cowl andthrust reverser system utilized with the engine of FIG. 1;

FIG. 3 is a simplified functional schematic representation of anexemplary thrust reverser control system according to an embodiment ofthe present invention;

FIG. 4 is a cross section view of an actuator element utilized in thethrust reverser control system depicted in FIG. 3;

FIG. 5 a simplified schematic representation of the thrust reversercontrol system depicted in FIG. 3, including a functional block diagramof a portion of the controller circuit; and

FIG. 6 is a flowchart depicting the method of controlling the deploymentof the thrust reversers according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Before proceeding with the detailed description of the invention, it isto be appreciated that the present invention is not limited to use inconjunction with a specific thrust reverser system design. Thus,although the present invention is explicitly described as beingimplemented in a cascade-type thrust reverser system, in whichtranscowls are used as the moveable thrust reverser component, it willbe appreciated that it can be implemented in other thrust reversersystem designs.

Turning now to the description, and with reference first to FIG. 1, aperspective view of portions of an aircraft jet engine fan case 10 thatincorporates a cascade-type thrust reverser is depicted. The engine fancase 10 includes a pair of semi-circular transcowls 12 that arepositioned circumferentially on the outside of the fan case 10.

As shown more particularly in FIG. 2, the transcowls 12 cover aplurality of cascade vanes 14, which are positioned between thetranscowls 12 and a bypass air flow path 16. When in the stowedposition, the transcowls 12 are pressed against one or more stow seals.The stow seals prevent air from flowing through the transcowls 12 whenthe thrust reversers are in the stowed position. A series of blockerdoors 18 are mechanically linked to the transcowls 12 via a drag linkthat is rotatably connected to an inner wall that surrounds the enginecase. In the stowed position, the blocker doors 18 form a portion of theinner wall and are therefore oriented parallel to the bypass air flowpath 16. When the thrust reversers are commanded to deploy, thetranscowls 12 are translated aft, causing the blocker doors 18 to rotateinto a deployed position, such that the bypass air flow path 16 isblocked. This also causes the cascade vanes 14 to be exposed and thebypass air flow to be redirected out the cascade vanes 14. There-direction of the bypass air flow in a forward direction creates areverse thrust and, thus, works to slow the airplane.

One or more actuators 28 per engine are used to operate the transcowls12. The actuators 28 are mounted to a stationary torque box 32 and eachincludes an actuator element 34, such as a ball screw, that is connectedto the transcowls 12. The actuators 28 interconnect with each other viaa synchronization mechanism, such as a plurality of flexible shafts 36.The flexible shafts 36 ensure that the actuators 28 move at the samerate. Thus, when the actuators 28 rotate, the actuator elements 34 andthe connected transcowls 12 are caused to translate at the same rate.

A control system controls movement of the transcowls 12 from a lockedand stowed position to an unlocked and deployed position for producingreverse thrust, and returns the transcowls 12 from the deployed positionback to the stowed and locked position. A simplified functionalschematic representation of an exemplary thrust reverser control systemis depicted in FIG. 3. The control system 40 includes a plurality ofactuators 28, each connected to a transcowl 12 by a respective actuatorelement 34, and interconnected by a plurality of flexible shafts 36.Each of the plurality of actuators 28 is driven by an electric motor 42,that is controlled by a controller circuit 44. Additional details of thecontroller circuit 44 and its operation will be discussed in more detailherein below. A plurality of locking mechanisms, including at least aprimary lock 46 and a secondary lock 48, prevent unintended movement ofthe transcowls 12 from the stowed position.

A position sensing device 52 is used to sense the position of thetranscowls 12. In a preferred embodiment, the position sensing device 52is a limit switch that senses at least when the transcowls 12 attain apredetermined position, which will be discussed more fully below. Itwill, however, be appreciated that the position sensing device 52 is notlimited to a limit switch. Rather, numerous other position sensingdevices known in the art, non-limiting examples of which include anoptical sensor, an LVDT, an RVDT, and a potentiometer, may also be used.

A preferred embodiment of an actuator 28 and an actuator element 34utilized in the thrust reverser control system 40 is depicted in FIG. 4and, for completeness of understanding, will now be discussed. Theactuator 28 includes an input shaft 29 coupled to an unillustratedflexshaft 36. The input shaft 29 includes gearing 31 that mates with abevel gear 33. The bevel gear 33 is coupled to a ball screw shaft 35,which is rotationally supported by a first duplex bearing assembly 37. Afirst end 41 of the ball screw shaft 35 is connected, via a gimbal mount43, to the forward end of the engine nacelle support (not illustrated).A second end 45 of the ball screw shaft 35 is rotationally supported bya second duplex bearing assembly 37′, which is connected to the aft endof the nacelle support (not illustrated). A ball nut 47, which isrotationally supported on the ball screw shaft 35 by a plurality of ballbearings 49, is attached to the transcowl 12 (not illustrated). Thus,rotation of the ball screw shaft 35 results in translation of the ballnut 47 and transcowl 12. A mechanical hard stop 51, positioned proximatethe second duplex bearing assembly 37′, stops translation of the ballnut 47, and thus the attached transcowl 12, in the deploy direction 53.

Turning now to FIG. 5, which depicts a simplified schematicrepresentation of the thrust reverser control system 40, along with afunction block diagram of a portion of the controller circuit 44, adiscussion of a preferred embodiment of the present invention will beprovided. As depicted in FIG. 5, the controller circuit includes anoutput port 54 that is electrically coupled to the motor 42. Thecontroller circuit further includes at least three input ports, whichaffect how the controller circuit 44 controls the operation of the motor42. Specifically, the controller circuit 44 includes an ENABLE port 56,a MOTOR SPEED COMMAND port 58, and a MOTOR SPEED FEEDBACK port 62.

The ENABLE port 56 controls whether the controller circuit 44 canprovide power to the motor 42. For example, if the controller circuit 44is designed to operate in a “positive logic” scheme, then a logic “high”signal at the ENABLE port 56 enables the controller circuit 44 toprovide power to the motor 42, whereas a logic “low” disables thecontroller circuit 44 from doing so. Conversely, if the controllercircuit 44 is designed to operate in a “negative logic” scheme, then alogic “low” signal at the ENABLE port 56 enables the controller circuit44 to provide power to the motor, and a logic “high” disables thecontroller circuit 44. In either case, a comparator circuit 72, such asa hysteretic comparator, includes an output that is electrically coupledto the ENABLE port 56. As will be discussed more fully below, thecomparator circuit 72 supplies the appropriate logic level signal to theENABLE port 56 to enable or disable the controller circuit 44.

The signal supplied to the MOTOR SPEED COMMAND port 58 sets the targetrotational speed at which the controller circuit 44 will cause the motor42 to rotate. A plurality of speed command signals are available to beselectively coupled to the MOTOR SPEED COMMAND port 58. In a preferredembodiment, the plurality of speed command signals include a “zero”speed command signal and a “non-zero” (or high) speed command signal.When the non-zero speed command signal is coupled to the MOTOR SPEEDCOMMAND port 58, the controller circuit 44 (when enabled) sets thetarget rotational speed of the motor 42 to a non-zero magnitude.Conversely, when the zero speed command signal is coupled to the MOTORSPEED COMMAND port 58, the controller circuit 44 (when enabled) sets thetarget rotational speed of the motor 42 to zero. The circumstances underwhich the zero and non-zero speed command signals are coupled to theMOTOR SPEED COMMAND port 58 are discussed more fully below. The skilledartisan will, however, appreciate that this particular non-zerorotational speed magnitude is only exemplary of a preferred embodiment,and that the magnitude may be varied to acheive desired system response.The particular motor 42 may be one of numerous motor designs known inthe art, including both DC and AC motors. The particular motor designand non-zero rotational speed magnitude are design variables chosen tomeet the requirements of the particular thrust reverser system.

The MOTOR SPEED FEEDBACK port 62 is coupled to receive a speed signalfrom a speed sensor 64. The speed sensor 64 is connected to sense therotational speed of the motor 42, and may be any one of numerousrotational speed sensors known in the art. In a preferred embodiment,however, the sensor 64 is a resolver unit coupled to the motor 42. Inany event, the signal from the speed sensor is coupled to the MOTORSPEED FEEDBACK port 62 and is compared, within the controller circuit44, to the speed command signal coupled to the MOTOR SPEED COMMAND port58. The result of the comparison determines the magnitude of the currentapplied to the motor 42. For example, if the signal from speed sensor 64indicates that the motor 42 is rotating faster than what is commanded onthe MOTOR SPEED COMMAND input port 58, then the current magnitudesupplied to the motor 42 is adjusted to cause the motor speed todecrease. Conversely, if the signal from the speed sensor 64 indicatesthat the motor is rotating slower than what is commanded, the currentmagnitude supplied to the motor 42 is adjusted to cause the motor speedto increase. Thus, the controller circuit 44, when enabled, controls therotational speed of the motor 42 via this closed loop feedback controlconfiguration.

Having described the thrust reverser control system 40 specifically froma structural standpoint, and generally from an functional standpoint, aspecific description of a particular functional aspect of the presentinvention will now be provided. In this regard, reference should now bemade to FIGS. 5 and 6 in combination, while a description of adeployment operation of the thrust reverser system is provided. Thisdescription is predicated on the thrust reverser system initially beingin the stowed position, and is being moved to the deployed position.Additionally, the partenthetical references to “STEPs” correspond to theparticular reference numerals of the methodological flow 100 depicted inFIG. 6.

With the above-described background in mind, the description of thedeployment operation 100 will now be provided. When the aircraft touchesdown and the thrust reversers are needed, the pilot commands the thrustreversers to move to the deployed position (STEP 102). At this point,the target rotational speed of the thrust revereser motor 42 is set tothe non-zero magnitude by coupling the non-zero speed command to theMOTOR SPEED COMMAND port 58 (STEP 104). Thus, the motor 42 is energizedto rotate in the deploy direction with a current magnitude sufficient torotate at the non-zero target speed (STEP 106), causing the actuators 28to rotatate, which in turn causes the actuator elements 34 to translatethe connected transcowls 12 toward the deployed position.

While the transcowls 12 are translating toward the deployed position,the position sensing device 52 senses whether or not the transcowls 12have attained a predetermined position relative to the fully deployedposition (STEP 108). It is noted that, in a preferred embodiment, thepredetermined position is within 10% of the fully deployed position;however, the invention is not limited to this particular predeterminedposition. The motor 42 continues to translate the transcowls 12 towardthe deployed position, while being controlled to rotate at the non-zerorotational speed, until the predetermined position is attained.

As mentioned briefly above, the comparator circuit 72 supplies theappropriate logic level signal to the ENABLE port 56 to enable ordisable the controller circuit 44. This logic level is based upon acomparison made by the comparator circuit 72. Specifically, thecomparator circuit 72 receives the rotational speed sensed by the motorspeed sensor 64 and determines whether the rotational speed of the motor42 is at or above a first predetermined speed, or at or below a secondpredetermined rotational speed. If the rotational speed of the motor, assensed by the speed sensor 64, is at or above the first predeterminedspeed, then the comparator circuit 72 outputs the appropriate logiclevel signal to enable the controller circuit 44 to decelerate themotor. Conversely, if the speed sensor 64 senses that the motor speed isat or below the second predetermined speed, then the comparator circuit72 outputs the appropriate logic level signal to disable the controllercircuit 44. The reason behind this particular functionality will becomemore apparent from the descriptions below. In a preferred embodiment thefirst predetermined rotational speed is set to 1000 r.p.m., and thesecond predetermined rotational speed is set to 300 r.p.m. It will beappreciated that other values may be selected for the first and secondpredetermined rotational speeds, as well as other numbers ofpredetermined rotational speeds for comparison, in order to meet arequired system response.

Since the comparator circuit 72 continuously receives the sensed motorrotational speed from the sensor 64, the comparator circuit 72 performsthe above-described functionality while the transcowls 12 aretranslating to the predetermined deployed position. As long as the motorspeed remains above the second, lower predetermined rotational speed,the controller circuit 44 will remain enabled and, thus, the motor 42will remain energized to rotate at the non-zero rotational speed.Otherwise, if the motor speed is below the second predeterminedrotational speed, the controller circuit 44 will be disabled, and themotor 42 will be deenergized. Considering the magnitudes of the firstand second predetermined rotational speeds relative to the non-zerotarget rotational speed, the comparator circuit 72 will continue toenable the controller circuit 44, at least until the predeterminedposition is attained, unless the system malfunctions.

Once the predetermined position is attained, the target rotational speedof the motor is set to zero (STEP 112), and the motor is subsequentlyenergized with a current magnitude sufficient to cause the motor todecelerate to zero r.p.m. (STEP 114). The hysteretic comparator 72monitors the speed of the motor 42, via the speed sensor 64, todetermine whether the rotational speed of the motor 42 is at or abovethe first predetermined speed (STEP 116) or at or below the secondpredetermined rotational speed (STEP 118). As long as the rotationalspeed of the motor is at or above the first, upper predeterminedrotational speed, the controller circuit 44 will be enabled and willenergize the motor 42 with a current to decelerate the motor 42. Oncethe rotational speed of the motor 42 is at or below the secondpredetermined rotational speed, the hysteretic comparator 72 disablesthe controller circuit 44, which in turn deenergizes the motor 42 (STEP122). If the actuator elements 34 have not reached the hard stops 51,then the aerodynamic loads will cause the motor 42 to free-wheel andaccelerate. If the motor 42 is caused to accelerate up to the secondpredetermined rotational speed (STEP 116), then the hystereticcomparator 72 will once again enable the controller circuit 44, whichwill energize the motor with a current magnitude sufficient todecelerate the motor to zero r.p.m. (STEP 114).

The above-described limit cycle will continue until the actuatorelements 34 reach the hard stops 51. Once this occurs, the motor 42 willno longer be accelerated by the aerodynamic loads when deenergized, thehysteretic comparator 72 will maintain the controller circuit 44disabled, and the motor 42 will remain deenergized.

As indicated previously, the present invention is not limited to usewith a cascade-type thrust reverser system, but can be incorporated intoother thrust reverser design types. Moreover, the methodology of thepresent invention is not limited to use with an electric orelectromechanical thrust reverser actuation system. Rather, themethodology of the present invention can be incorporated into otheractuation system designs, including hydraulic and pneumatic.

Additionally, the circuit components of the present invention are notlimited to that explicitly depicted herein. Indeed, the circuitcomponents may be formed of either discrete components, or incorporatedinto a single integrated circuit. Moreover, the process carried out bythe electrical components may be realized using software driven devices,or it may be carried out using analog devices and signals, or acombination of both.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt to a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe appended claims.

I claim:
 1. A jet engine thrust reverser control system, comprising: an electric motor; one or more moveable thrust reverser components coupled to the motor, the components moveable between a stowed position and a deployed position; a speed sensor operable to sense at least a rotational speed of the motor and produce a speed feedback signal; and a controller circuit coupled to receive at least the speed feedback signal and being operable in response thereto to energize and deenergize the motor when the rotational speed of the motor is, respectively, at or above a first predetermined rotational speed and at or below a second predetermined rotational speed.
 2. The system of claim 1, further comprising: a comparator circuit having an input coupled to receive at least the speed feedback signal and an output coupled to the controller circuit, the comparator circuit being operable to compare the speed feedback signal with the first and the second predetermined rotational speeds and to enable the controller circuit when the rotational speed of the motor is at or above the first predetermined rotational speed and to disable the controller circuit when the rotational speed of the motor is at or below the second predetermined rotational speed.
 3. The system of claim 1, wherein the controller circuit includes a motor speed command input port coupled to receive one of a plurality of motor speed command signals, and wherein the controller, when selectively energizing the motor, causes the motor to rotate in accordance with the received motor speed command signal.
 4. The system of claim 3, wherein the plurality of motor speed command signals includes at least a zero speed command signal and a non-zero speed command signal.
 5. The system of claim 4, further comprising: a position sensor operable to sense at least when the one or more moveable thrust reverser components attain a predetermined position relative to the deployed position, wherein the motor speed command input port is coupled to receive the zero speed command signal in response to the position sensor sensing that the predetermined position is attained.
 6. The system of claim 1 wherein the motor speed sensor comprises a motor resolver unit.
 7. The system of claim 5, wherein the position sensor comprises a limit switch.
 8. The system of claim 5, wherein the position sensor is selected from the group consisting of an LVDT, an RVDT, an optical sensor, and a potentiometer.
 9. The system of claim 1, wherein the motor is coupled to the one or more moveable thrust reverser components via one or more actuator elements.
 10. The system of claim 5, wherein the predetermined position is a position within 10% of a fully deployed position.
 11. The system of claim 1, wherein the first predetermined rotational speed is greater than the second predetermined rotational speed.
 12. A jet engine thrust reverser control system, comprising: an electric motor; one or more moveable thrust reverser components coupled to the motor, the components moveable between a stowed position and a deployed position; a speed sensor operable to sense at least a rotational speed of the motor and produce a speed feedback signal; a controller circuit having an output coupled to the motor for energizing the motor when the controller circuit is enabled; and a comparator circuit having an input coupled to receive at least the speed feedback signal and an output coupled to the controller circuit, the comparator circuit being operable to compare the speed feedback signal with first and second predetermined rotational speeds and to enable the controller circuit when the rotational speed of the motor is at or above the first predetermined rotational speed and to disable the controller circuit when the rotational speed of the motor is at or below the second predetermined rotational speed.
 13. The system of claim 12, wherein the controller circuit includes at least a motor speed command input port coupled to receive one of a plurality of motor speed command signals and wherein the controller, when enabled, causes the motor to rotate in accordance with the received motor speed command signal.
 14. The system of claim 13, wherein the plurality of motor speed command signals includes at least a zero speed command signal and a non-zero speed command signal.
 15. The system of claim 14, further comprising: a position sensor operable to sense at least when the one or more moveable thrust reverser components attain a predetermined position relative to the deployed position, wherein the motor speed comand input port is coupled to receive the zero speed command signal in response to the position sensor sensing that the predetermined position is attained.
 16. The system of claim 12 wherein the motor speed sensor comprises a motor resolver unit.
 17. The system of claim 15, wherein the position sensor comprises a limit switch.
 18. The system of claim 15, wherein the position sensor is selected from the group consisting of an LVDT, an RVDT, an optical sensor, and a potentiometer.
 19. The system of claim 12, wherein the motor is coupled to the one or more moveable thrust reverser components via one or more actuator elements.
 20. The system of claim 15, wherein the predetermined position is a position within 10% of a fully deployed position.
 21. The system of claim 12, wherein the first predetermined rotational speed is greater than the second predetermined rotational speed.
 22. A jet engine thrust reverser control system, comprising: an electric motor; one or more moveable thrust reverser components coupled to the motor, the components moveable between a stowed position and a deployed position; a speed sensor operable to sense at least a rotational speed of the motor and produce a speed feedback signal; a position sensor operable to sense at least when the one or more moveable thrust reverser components attain a predetermined position relative to the deployed position; a controller circuit including at least (i) a motor speed command input port coupled to receive one of a at least a zero speed command signal and a non-zero speed command signal and (ii) an output coupled to the motor for selectively energizing the motor to rotate in accordance with the received motor speed command signal; and a comparator circuit having an input coupled to receive at least the speed feedback signal and an output coupled to the controller circuit, the comparator circuit being operable to compare the speed feedback signal with first and second predetermined rotational speeds and to enable the controller circuit when the rotational speed of the motor is at or above the first predetermined rotational speed and to disable the controller circuit when the rotational speed of the motor is at or below the second predetermined rotational speed, thereby causing the controller circuit to selectively energize the motor, wherein the motor speed command input port is coupled to receive the zero speed command signal in response to the position sensor sensing that the predetermined position is attained.
 23. The system of claim 22 wherein the motor speed sensor comprises a motor resolver unit.
 24. The system of claim 22, wherein the position sensor comprises a limit switch.
 25. The system of claim 22, wherein the position sensor is selected from the group consisting of an LVDT, an RVDT, an optical sensor, and a potentiometer.
 26. The system of claim 22, wherein the motor is coupled to the one or more moveable thrust reverser components via one or more actuator elements.
 27. The system of claim 22, wherein the predetermined position is a position within 10% of a fully deployed position.
 28. The system of claim 22, wherein the first predetermined rotational speed is greater than the second predetermined rotational speed.
 29. A jet engine thrust reverser control system, comprising: moving means for moving one or more moveable thrust reverser components between a stowed position and a deployed position; speed sensing means for sensing at least a rotational speed of the moving means; and controller means for (i) energizing the moving means when the speed sensing means senses that the rotational speed of the moving means is at or above a first predetermined rotational speed and (ii) deenergizing the moving means when the speed sensing means senses that the rotational speed of the moving means is at or below a second predetermined rotational speed.
 30. The system of claim 29, further comprising: comparison means for (i) comparing the sensed rotational speed from the speed sensing means with the first and second predetermined rotational speeds and (ii) enabling the controller means when the rotational speed of the moving means is at or above the first predetermined rotational speed and disabling the controller means when the rotational speed of the moving means is at or below the second predetermined rotational speed, thereby causing the controller means to selectively energize and deenergize the moving means.
 31. The system of claim 29, wherein the controller means includes a speed command input port coupled to receive one of a plurality of speed command signals, thereby establishing a target rotational speed and wherein the controller means, when energizing the moving means, causes the moving means to rotate at the target rotational speed.
 32. The system of claim 31, wherein the plurality of speed command signals includes at least a zero speed command signal and a non-zero speed command signal.
 33. The system of claim 32, further comprising: position sensing means for (i) sensing at least when the one or more moveable thrust reverser components attains a predetermined position relative to the deployed position and (ii) coupling the motor speed comand input port to receive the zero speed command signal in response to the position sensing means sensing that the predetermined position is attained.
 34. The system of claim 29, wherein the moving means is coupled to the one or more moveable thrust reverser components via one or more actuator elements.
 35. The system of claim 33, wherein the predetermined position is a position within 10% of a fully deployed position.
 36. The system of claim 29, wherein the first predetermined rotational speed is greater than the second predetermined rotational speed. 